Wear and stretch compensating control arrangement for variable speed belt drive



Jan; 12, 19

Filed Dec. 15

60 pmDER 2,920,493

J. M. WEAR AND STRETCH COMPENSATING CONTROL ARRANGEMENT FOR VARIABLE SPEED BELT DRIVE 1958 3 Sheets-Sheet l INVENTOR. JAMES M. P INDER HIS ATTORNEY Jan. 12, 1960 Filed Dec. 15. 1958 J. M. FINDER WEAR AND STRETCH COMPENSATING CONTROL ARRANGEMENT FOR VARIABLE SPEED BELT DRIVE 3 Sheets-Sheet 2 5 20 58 29 I o l, I I4 6 1? 71 j Z n 63 75 74 7s 66 62 z 64 INVENTOR.

JAMES M. FINDER WWW H [S ATTORNEY Jan. 12, 1960 pm 2,920,493

WEAR AND STRETCH COMPENSATING CONTROL ARRANGEMENT FOR VARIABLE SPEED BELT DRIVE Filed Dec. 15, 958

3 Sheets-Shet 3 INVENTOR.

TAME M- FINDER BY fle United States Patent WEAR AND STRETCH COMPENSATING CONTROL ARRANGEMENT FOR VARIABLE SPEED BELT DRIVE James M. Pinder, Louisville, Ky., assignor to General Electric Company, a corporation of New York Application December 15, 1958, Serial No. 780,294 5 Claims. (Cl. 74-23017) This invention relates to variable speed belt drives of the typewhich may be used for rotating the clothes container in domestic laundry machines, and more particularly to a compensating control arrangement for preventing substantial variation of the rotational speed imparted to the driven element as a result of wear of the belt and sheave parts of such drives.

Domestic laundry machines generally provide a sequence which includes a washing cycle, at least one n'nse cycle to get rid of the washing liquid, and a centrifuging spin operation to remove liquid from the clothes after the rinse operation. In many domestic machines, particularly those which have a clothes container rotatable on a non-vertical axis, the washing and rinsing steps are provided by relatively slow rotation of the container (which provides a tumbling pattern for the clothes) and the centrifuging step is provided by a high speed operation of the container. In those laundry machines which combine the function of washing machines and drying machines, that is, where the same machine washes the clothes and then dries them completely, the aforementioned steps are generally immediately followed by a drying operation which consists of providing heat to vaporize moisture from the clothes as they are tumbled in the clothes receptacle.

It is important for a full understanding of the present invention to know that the speed of rotation of the clothes container is of critical importance, both as to the quality of the washing action of the machine and as to the most appropriate tumbling pattern during the heat drying operation. For instance, in a machine having a twenty-six inch cylindrical clothes container rotatable about its longitudinal axis, it has been found that a rotationalspeed of about 49 rpm. provides the optimum clothes washing effect, while a speed of 45 rpm. provides the optimum tumbling speed for drying. In many of the machines which combine the two functions, a single compromise speed of 47 r.p.m. has been provided for both the washing operation and the heat drying operation- In order to facilitate attainment of various speeds such as, for instance, a low speed suitable for washing and for drying, and one or more spin speeds, severalcommercially available domestic laundry machines have adopted, as part of their drive systems, variable sheave belt drive arrangements wherein the radius from the center of rotation of the sheave to the seat of the belt in the sheave groove may be varied for either the driven sheave, the driving sheave, or both. Such variable sheave belt drives include appropriate means for stopping the variation of the sheave formation when the desired speed has been attained. However, to the applicants knowledge, such arrangements have not heretofore included any auto matic compensation for belt wear or belt stretch, both of which independently have an effect on the .speed of rotation in variable speed belt drives, and which together can have a cumulative efiect. While for many applications small variations in the speedofrotation of thedriven 2,920,493 Patented Jan. 12, 1960 member can be overlooked, there are other applications such as in the domestic laundry field where, as set forth above, the tumbling speed of the container is quite critical. For this reason it becomes important, where variable speed belt drives are used for the transmission of power in machines where speed is critical, such as domestic laundry machines, to provide a suitable compensating arrangement so that wear and stretch of the belt will not have the undesirable effect of varying the speed of rotation of the container, or basket.

It is, accordingly, a primary object of this invention to provide an improved compensating control arrangement for use in variable speed belt drives, particularly where they are intended to be used in domestic laundry machines, for greatly reducing variation of the speed from that desired as a result of belt wear and belt stretch.

A further object of the invention is to provide a particular compensating arrangement which is directed to the problem of belt wear so as to eliminate variations of the speed output which might otherwise result therefrom.

Yet another object of the invention is to provide a particular compensating arrangement for belt stretch so as to preclude speed variations in the output of the drive as the result of the stretch factor of the aging of the belt.

In one aspect thereof, my invention provides a variable speed belt drive mounted in the usual manner on an appropriate base. A first pair of axially aligned sheave plates are rotatably mounted on the base, and form a generally V-shaped annular groove between them, this first pair of plates is driven by appropriate means at a substantially constant speed, and thus they constitute the input or driving sheave. A second pair of axially aligned sheave plates is also rotatably mounted on the 'base with the axis of rotation of the plates located a predetermined distance from the axis of rotation of the first pair, and likewise forms a generally V-shaped annular groove. An endless flexible belt is seated in the grooves of the two pairs of plates and links them so that the sheave formed by the second pair is driven by this arrangement and can be used to cause rotation of the desired driven means. The belt has a generally V-shaped cross section (in most commercial applications, the cross section is that of a truncated V) so as to fit suitably in the annular grooves of the two pairs of sheave plates.

In order to vary the speed output without variation of the speed input, means are provided for axially moving one plate of one of the pairs relative to the other plate thereof so as to change the depth at which the belt is seated in the groove formed by the one pair of sheave plates; this varies the speed of rotation of the output pair of plates because the effective diameter of the one pair is changed as a result of the belt being seated at a. greater or lesser depth in the groove thereof. Means are provided so as to yieldably bias the plates of the other pair of sheave plates toward each other; this corrects the spacing of the other pair of plates in response to an axial adjustment of the one pair.

In order to control the axially movable means so as to return the second pair of sheave plates to the same output speed regardless of belt wear, means are arranged adjacent one pair of plates to sense the distance from the center of rotation thereof to the outer surface of the belt where it is seated in the groove formed by that adjacent pair. The control means stops the operation of the axially moving means when the distance sensed is a predetermined amount, thus making the efiective radius of rotation of the sheave formed by the adjacent pair of plates the dominant factor regardless of the amount of belt wear. In other words, as the belt wears, the two adjacent plates of the sheave will be moved closer together to provide the same depth'of'the belt in the groove, thereby to compensate for the wear of the .belt.

Qrelation tothe first pair of plates.

Inlaundry machine drives including the arrangement briefly described above, the sheave formed by the second pair of plates will generally be formed in a unitary assemblywith a pulley which, through a belt and a driven pulley, rotates the clothes basket. Where this construction used, I provide means to achieve compensation 'for the stretch of the belt linking the two pairs of plates.

fThe assemblyof the output pair of sheave plates and pulley is secured on the base in a predetermined movable It is held at a fixed distance from .the first pair by, first, the combined motion-limiting action of the belt linking the driven basket pulley with the pulley attached to the output pair of sheave plates and, second, by suitable spring means which bias the assembly away both from the input pair of plates and, from the driven pulley. It has been determined that different belts in thesame system stretch at an approximately proportional rate of speed. The predetermined pathof movement of the assembly is selected to take advantage of this fact; in other words, since it is known approximately how much the belt linking the pairs of plates will stretch fora given amount of stretch of the driven pulley belt, the path of movement of the assembly is selected to compensate for the plate belt stretch in response to stretchingof the pulley belt.

The subject matter which constitutes the invention is particularly pointed out and distinctly claimed in the coneluding portion of this specification. The invention itself, however, both as to organization and method of operation together with further objects and advantages thereof, may best be understood by reference to the following description taken in conjunction with the accompanying drawings in which:

Figure l is a side elevational view of a domestic laundrymachine of the type which both washes and dries completely, partly in section and with certain surfaces broken away to show details; Figure 2 is a rear elevational view of the machine of Figure '1 with the rear panel removed to illustrate details;

Figure 3 is a fragmentary side elevational view of the other side of the machine from that shown in Figure 1, with certain surfaces broken away to show further details; 1

1 Figure 4 is an enlarged fragmentary view of part of the improved compensating arrangement ofv this invention; and

Figure 5 is a schematic illustration of the speed control circuit used in' connection with the structure illustrated in Figures 1, 2, 3 and 4.

: Referring now to Figures 1- and 2, there is shown a combination washer dryer machine where the operating elements of the machine are included within an outer cabinet structure which has a wrap-around central section 1 supported on a base and toe board assembly 2 and carrying a separate top 3 provided with an integral backsplash panel -4. Access to the interior of the machine is provided by a door 5 mounted on concealed hinges and opened by any suitable means such as, for instance, knee operated latch control 6. The machine is so constructed that when a load of soiled clothes is placed therein it proceeds through a sequence of operations, first washing the clothes and then drying them. In order to provide flexibility of operation of the machine, suitable operator controls may be included therein, the controls being mounted on the backsplash panel -4. Illustrative of these controls is a suitable dial 6, shown on the backsplash panel, for convenient operator selection of any separate sequence of operations.

, As shown in the figures, the machine is of the horizontal axis type, that is, it has a clothes basket or receptacle 7 mounted for rotation on a generally horizontal axis within an outer enclosing tub structure 8. Basket 7 includesv a cylindrical shell or wall 9, and a front wall 10 which formed so as to define an access or loading opening 10a to the basket. The basket is .rotatably' supported by a shaft 11 which is mounted in an elongated bearing 12 supported from rear wall 13 of the tub. The tub is provided with an opening 13a in the front wall thereof which is aligned with the access opening to the basket so that clothes may be placed into and removed from the basket. Door '5 seals against a suitablegasket 13b to close this opening during operation of the machine.

During the operation of the machine, the basket 7 is driven from an electric motor 14 mounted to tub 8 by bracket 14a. Thus, the tub provides the base to which the drive including motor 14 is mounted. The drive from the motor to the basket includes a pulley 15 which is secured to the motor shaft so as to rotate therewith and over which passes an endless flexible belt 16 which drives a pulley 17. Pulley 17 is mounted on the same shaft 18 as two sheave plates 19 and 20 which are axially movable relative to each other. This is effected, in the present case, by making plate 20 axially slidable on shaft '18 although rotatable therewith. Plate 20 is biased toward plate 1 9 by a spring member 21 mounted on shaft 18, as shown in Figure l. Sheave plate 19 has a sloping surface 22, and plate 20 has a similar surface 23, so, that between them surfaces 22 and 23 form a groove of generally V-shaped cross section.

Seated. in the groove 24 formed by surfaces 22 and 23 is an endless flexible belt 25 having a cross section substantially in the form of a truncated V whose sides engage the sides of the groove so that rotation of plates 19 and 20 drives the belt 25. Belt 25 also passes within the groove 26 formed by the surfaces 27 and 28 of a pair of sheave plates 29and 30 which are secured to a rotatably mounted hollow shaft 31; plates 29 and 30, while rotatable together, are axially movable relative to .each other.

In the case of plates 29 and 30, the axially movable relationship .is obtained by making plate 30 axially movable along shaft 31. This is achieved by providing a sleeve 32 over the shaft secured to plate 30' so that when sleeve 32 is moved axially it carries the plate with it. Separated from sleeve 32 by a thrust bearing 32a is a nut member 33 having an exterior surface 34 formed as a gear and positioned to be engaged by a pinion member 35 driven through a conventional motor and gear train assembly 36. Mechanical connection of gear 34 to motor and gear train assembly 36 can best be seen by reference to Figure 4. r

The internal surface of the nut member 33 is threaded, andengages the mating threaded end 37 of a shaft 38 non-rotatably secured in fixture 39 (Figure 3) fastened to tub wall 8 Shaft 38 provides the base on which hollow shaft 31 is rotatably mounted a fixed predetermined distance from shaft 18. Upon rotation of pinion 35 by motor 36, nut member 33 is caused to rotate and therefore, by its threaded engagement with end 37 of shaft 38, to move axially on the shaft in one direction or the other depending upon the direction of rotation of the pinion 35.- The nut member in moving axially carries with it the sleeve 32 and the plate 30 so as to vary the width of groove 26. In addition, the friction eifect of belt 41.

brake when motor 36 is not energized and thus to hold plates 29 and 30 in the desired relationship.

Secured on 'shaft 31 so as to rotate with plates 29 and 30 is a pulley 40 which is in driving relationship to a Beltf41 in turn drives a pulley 42 which is secured. on shaft-llso that rotation of the pulley 42 causes a corresponding rotation of basket 7. Thus, to recapitulate briefly, starting with motor 14 the drive proceeds through pulley 15, belt 16, pulley 17, sheave plates 19 and 20, belt '25, sheave plates 29 and 30, pulley 4.0,belt 41, pulley 42, shaft 11, and basket 7. A lower, orltumble speed of about 47 r.p.m. for the construction shown, wherein a container having a diameter of about 26 ,inchesis .used, isobtained with the adjustable plates in the position shown, i.e., with plates 29 and 30 close to each other to force belt 25 outwardly. in groove 26 andwith' the belt "correspondingly pulled inwardly at plates 19 and 20 to widen groove 24; To increase the speed to efiect a centrifugal spin operation, moved away from plate '29 to widen groove 26 and allow belt to move radially inwardly toward the center of rotation of shaft 31; this permits spring 21 to push plate 20 toward plate 19 to force belt 25 outwardly in groove 24.

To complete the general understanding of the functioning of the illustrated laundry machine, the remainder of the conventionally provided parts will be briefly set forth prior to describing the application of the improved compensating and control arrangement to the variable speed belt drive described.

To heat the clothes during the drying portion of the cycle, and also to warm the wash water during the washing portion of the cycle when desired, there is provided in the machine a heater assembly including two heaters 43 and 44. These heaters are mounted within the upper portion of tub 8 so that when energized they heat the basket 7. The heating elements are preferably of the sheathed type in which a resistance wire is maintained in spaced relation with an outer sheath by a highly compressed granulated heat-conducing electricallyinsulating compound such as magnesium oxide. When the heaters are energized during the washing cycle, they heat the water by first heating the basket. Then, as the basket dips into the Wash Water at the bottom of the tub, it in turn heats the water. In other words, the rotating basket serves as an effective heat transfer means between the heating elements and the water or other washing liquid. When the heaters are energized during the drying cycle, the heat transferred to the clothes basket is then passed on to the clothes to cause vapor migration out of the clothes. Since the outer cylindrical wall of the basket is perforated by a great many small spaced openings 45, some of the heat from the heating elements passes directly to the clothes by radiation.

The means whereby the water is admitted to and discharged from tub 15 during operation of the machine is particularly shown in Figure 2. The water supply means includes connections 46 and 47 through which hot and cold water is supplied to the machine for the washing operation. A valve controlled by a solenoid 48 admits hot water to the machine and a valve controlled by an opposed solenoid 49 admits cold water to the machine. The hot and cold water valves under the control of the solenoids 48 and 49 discharge through a common outlet conduit 50, through a suitable air gap, and into a funnel 51 which discharges into a line 52 leading to the interior of tub 8 through a suitable connection 53. The air gap provided by the funnel 51 makes it impossible for water to be syphoned from the machine thereby to contaminate the incoming water supply line. In the illustrated machine a pressure actuated sensing device or water level control 54 controls both solenoids 48 and 49 to maintain the proper water level in the machine during the washing operation. This sensing device is connected to the interior of tub 8 by a suitable line 55.

.The illustrated machine is of the type which uses cold water during drying cycles for condensing the moisture extracted from the clothes. This condenser water is admitted to the machine through an additional solenoid-actuated valve controlled by a solenoid 56 (Figure 2). Solenoid 56 is energized during the drying operation so that the valve passes water at a slow rate sufficient to condense from the air the moisture vaporized from the clothes. As shown, the condenser water valve discharges into funnel 52 through a separate conduit 57, with an air gap between conduit 57 and the funnel preventing supply line contamination as before. From the funnel the condenser water flows through conduit 52 and connection 53 into the tub. The condenser water flowing slowly into the tub is spread over the side of the tub by an inverted V-shaped bead 58 (Figure 1) formed on the tub wall directly below the connection plate is 53. The condenser water being so spread out cools a substantial portion of the area of the side wall whereby there is provided a large cool surface for condensing the moisture extracted from the clothes.

The wash and rinse water used during the washing portion of the operation, and the condenser water and the moisture extracted from the clothes during the drying operation are discharged from the machine through a sump 58 mounted at the bottom of the tub. A suitable discharge hose 59 leads from the sump to suitable drain means (not shown) which are normally arranged to discharge to the household drain.

With the apparatus shown, any suitable sequence derived from the basic sequence of washing, rinsing and spinning may be utilized to eflect the washing portion of the cycle, and is followed by the tumbling of basket 7 with suitable heating of the clothes being provided by heating elements 43 and 44.

Referring now to Figure 2 in particular, and also to Figures 1 and 3, the improved control and compensating arrangement which this invention provides in connection with the conventional variable speed drive described above will now be explained. An idler or roller member 60 is arranged so as to contact the outer surface of the belt 25 at a point where it is seated in the groove 24 formed by plates 19 and 20. The roller is rotatably mounted on a member 61 which is lightly biased to a position where roller 60 is against the belt by a spring member 62 which is very weak compared to the spring member 21. As shown, both member 61 and spring 62 may be mounted on a pin 63 formed in a bracket 64 secured to base 2. At its upper limit, the member 61 actuates a switch 65 secured to the base, and at its lower limit it actuates a switch 66 secured to the base, i.e., when the belt 25 is moved inwardly in groove 24 a predetermined amount switch 65 is tripped, and when the belt 25 moves outwardly in groove 24 a predetermined amount switch 66 is tripped.

Referring to Figure 5, there is shown a simplified schematic illustration of the manner in which the switches 65 and 66 are used in the control of motor 36. A pair of conductors 67 and 68 are connected across an appropriate source of power (not shown) in the usual manner, and are used to energize a control 69 which may be of the type conventionally provided in laundry machines of the type illustrated. While such features have been eliminated from Figure 5 in order not to remove the emphasis from the inventive concept, it will be understood that control 69 is conventionally used for the control of all the electrical components of the machine such as motor 14, heaters 43 and 44, and solenoids 48, 49 and 56. In addition, of course, the control 69 is used to control the motor and gear train assembly 36 which is made reversible by any suitable means such as, for instance, in the manner illustrated by providing one winding 70 for one direction of rotation and a second oppositely arranged winding 71 for the other direction of rotation, with control 69 energizing the two windings alternatively. Switch 65 is in series with winding 70 and switch 66 is in series with winding 71.

Let it be assumed, for example, that the machine has proceeded under the control of control 69 through an appropriate washing and rinsing sequence, and it is appropriate for the spin step to be provided; control 69 will energize winding 71 of motor 36 and the motor will rotate in the appropriate direction to move plate 30 away from plate 29, thus permitting belt 25 to move inwardly in groove 26. Correspondingly, spring 21 pushes plate 20 toward plate 19 to force the belt 25 outwardly in groove 24. This action continues until member 61 engages switch 66 and actuates it to the open position. This then de-energizes winding 71 and motor 36 ceases to cause movement of plate 30.

Thus, in response to a predetermined position of roller 60, the speed changing mechanism ceases to change speed and retains the speed at'which the switch 66 was actuated. Since the efiective radius of the sheave formed by plates 19 and 20 is being measured for speed determining purposes, thus by-passing any problem created by the wear of the' belt, this speed will always be the same when the signal for the speed increase to spin speed is provided.

In other words, the direct sensing of the position of the belt relative to the center of rotation, i.e., going directly to measurement of the factor which determines the output speed from plates 19 and'20, causes the same speed to be imparted to plates 29 and 30 regardless of the Width of the belt and regardless of the fact that this width decreasesas the belt Wears. Otherwise, if the conventional approach of causing a predetermined amount of movement of plate '30 to provide a particular speed were used, there would be no compensation for the belt wear, and as belt decreases in width it would move inwardly in the groove for a given; axial distance between plates.

At the end of the spin operation, the control 69 energizes winding 70 of motor 36 to cause rotation in the direction to return the speed :to its low tumble level, that is, about 47 rpm. in the machine illustrated. Motor 36 now joperates to push plate toward plate 29 so as to force belt 25 outwardly in groove 25 and inwardly in groove '24. Roller follows belt 25 as it moves inwardly in groove 24 until switch 65. is actuated to its open position. As viewed in Figure 5, this immediately de-energizes Winding 70 and stops the motor 36. Thus, once again a predetermined speed dependent only on the efiective radius of the sheave formed by plates 19 and 21) independently of any belt wear which may occur. In the provision of tumble speed, this is of very great importance since the speed is, as explained above, a critical one. Tests have shown that during the normal operating life of a machine, belt wear may account for as much as seven or eight rpm. difference in the basket tumble speed unless compensated for. It will readily be seen that a decrease of the speed to 40 r.p.m. from the 47 rpm. intended would, in thelight of the critical nature of the tumble speed, have an adverse effect both for washing and for drying.

In order for the variable speed belt drive described to be operative, it is, of course, necessary that the shafts 18 and 31 be positioned a .predetermined distance apart. However, if this distance is absolutely immovably set, then the stretching of belt 25 which must inevitably occur as the belt ages, will also have an adverse eifect on the speed of the machine .by decreasing the speed in addition to that which would have been caused by wear if the compensating arrangement described above had not been provided. It therefore is desirable to compensate for belt stretch despite the fact the distance between the shafts of the two pairs of plates should be a predetermined one. In order to achieve this, I have taken advantage of the fact that a definite proportional relationship has been noted between the stretch of different pulley belts used in the same system. Thus there is a predetermined relationship in the stretch of belts 41 and 25 as they age, that is, for a predetermined amount of stretch of belt 41 there will also be a predictable predetermined amount of stretch in belt 25.. From this information, I have determined that the stretch of belt 41 may be used as the controlling factor in determining how much the shaft 31 should be moved relativeto shaft 18 to compensate for stretching of belt 25. i This eifect is provided in the present arrangement (see Figures land 4) by mounting the threaded end 37 of shaft 38 on a linkage'member 72. Member 72 is .pivotally mounted on a pin 73 secured in a bracket 74 which in turn is bolted to the wall of sump 58. Viewing Figure 4 in particular, it can thus be seen that the shaft 38 is supported on member 72 at its one end 37. As previously explained, at its other end it is supported in fastening 39 (Figure 3); fastening 39 is pivotally mounted to thewall of tube is a manner similar to that shown in Figure 4 for part 72, The assembly of plates 29 and 3t and pulley 40, in'turn, is mounted on shaft 31 which is rotatably secured in shaft 38 sothat the entire system of plates 29 and 30 and pulley 40 is in eifect pivotally mounted relative to the base 2. A suitable spring 75 is secured at one end 76 to the base 2,'and at its other end 77 to the sheave plate and pulley assembly so that the system is always spring biased in a clockwise direction about pin 73, as viewed in Figure 4, with the shaft 31 following a predetermined path as controlled by the position of pin 73 and the distance from the pin to the shaft. It will also be observed that spring 75 biases the assembly in a direction opposing the pull of both belt 25 and belt 41. I

With the arrangement shown, shaft 31 is in effect at a fixed distance from shaft 18 so long as there is no belt stretch; thus, the variable speed belt drive will operate in its ordinary fashion as described. However; when belt stretch occurs as a result of aging of the belts, belt 41 will lengthen a little thus permitting spring 75 to pull the entire assembly in a clockwise direction a minute amount. This then will also slightly increase thedista'nce between shafts 18 and 3 1. This latter increase will compensate for the stretch of belt 25 because of the proportional relationship which was predetermined to exist between belts 25 and 41. In other words, at the sametime that tension is maintained for belt 41, a corrective factor is provided for the stretch of belt 25 so as to maintain belt 25 in the same position within the groove 24 for a predetermined effective radius of the sheave formed by plates 29 and 30. In this manner, the effect of belt stretch is removed from the system and there will be practically no speed decrease through the life of the machine resulting from belt stretch, as there would have been if the corrective measure had not been taken based on the proportional relationship between the stretching of belts 25 and 41. While the amount of speed change resulting from belt stretching is generally smaller than that resulting from belt wear, perhaps on the order of 2 or 3 rpm,

such a change can neverthless detract from performance where a' critical speed is involved. It will be seen from the foregoing that the control arrangement provided compensates for both belt wear and belt stretch, thus making the speeds provided by the variable speed belt drive independent of these factors which invariably accompany aging of the belts. In this manner any critical speeds, such as the one used for tumbling the clothes, will be retained through the life of the machine.

While in accordance with the patent statutes I have described what at present is considered to be the preferred embodiment of my invention, it will be obvious to those skilled in the art that various changes and modificationsmay be made therein without departing from the invention, and I therefore aim in the appended claims to cover all such changes and modifications as fall within the true spirit and scope of the invention.

What I claim as new and desire to secure by Letters Patent of the United States is:'

1. A variable speed belt drive comprising a base, a first pair of axially aligned sheave plates rotatably mounted on said base and forming a generally V-shaped annular groove between them, driving means for rotating said first pair at a substantially constant speed, a second pair of axially aligned sheave plates rotatably mounted on said base with their axis of rotation a predetermined distance from the axis of rotation of said first pair and forming a generally V-shaped annular groove between them, an-endless flexible belt seated in said grooves and linking said two pairs of plates, said belt having a gen: erally V-shaped cross section, driven means rotated by said second pair, means for axially moving one plate of one of said pairs relative to the other plate thereof for changing the depth at which said belt is seated in the groove formed by said one pair thereby to vary the speed of rotation of said second pair, means yieldably biasing the plates of the other of said pairs toward each other to correct their, spacing in response to an axial adjustment of said one pair, and means adjacent one of said pairs for controlling said means for axially moving one plate to provide return of said second pair to a particular speed regardless of belt wear, said control means sensing the distance from the center of rotation of the pair to which it is adjacent to the outer surface of said belt where it is seated in the groove formed by said adjacent pair and stopping said means for axially moving one plate when said distance is a predetermined amount.

2. The apparatus defined in claim 1 wherein said means for axially moving one plate moves one plate of said second pair, and said yieldably biasing means biases the plates of said first pair toward each other.

3. The apparatus defined in claim 1 wherein said control means senses the distance of the outer surface of said belt from the center of rotation of said first pair.

4. A variable speed belt drive comprising a base, a first pair of axially aligned sheave plates rotatably mounted on said base and forming a generally V-shaped annular groove between them, driving means for rotating said first pair at a constant speed, a second pair of axially aligned sheave plates rotatably mounted on said base with their axis of rotation a predetermined distance from the axis of rotation of said first pair and forming a generally V-shaped annular groove between them, an endless flexible belt seated in said grooves and linking said two pairs of plates, said belt having a generally V-shaped cross section, driven means rotated by said second pair, means for axial-1y moving one plate of one of said pairs relative to the other plate thereof for changing the depth at which said belt is seated in the groove formed by said one pair thereby to vary the speed of rotation of said second pair, means yieldably biasing the plates of the other of said pairs toward each other to correct their spacing in response to an axial adjustment of said one pair, and means adjacent one of said pairs for controlling said means for axially moving one plate to provide return of said second pair to a particular speed regardless of belt wear, said control means comprising a follower member biased into engagement with the outer surface of said belt where it is seated in the groove formed by one of said pairs, switch actuating means movable with said follower member as it follows said belt surface during changes in the relationship of its associated pair of plates, a switch member positioned to be actuated by said actuating member when said follower member moves inwardly toward the center of rotation of said associated pair of predetermined amount, a second switch member positioned to be actuated by said actuating member when said follower member is moved away from the center of rotation of said associated pair a predetermined amount, each of said switches being connected to said means for axially moving the plate so that when actuated they stop operation of said means for axially moving one plate thereby to stop variation of the speed, whereby the distance of said follower member from the center of rotation of said associated pair of sheave plates controls the stopping of said means for axially moving one plate.

5. A variable speed belt drive comprising a base; a first pair of axially aligned sheave plates rotatably mounted on said base and forming a generally V-shaped annular groove between them; driving means for rotating said first pair at a constant speed; a second pair of axially aligned sheave plates rotatably mounted on said base with the axis of rotation thereof located a predetermined distance from the axis of rotation of said first pair and forming a generally V-shaped annular groove between them; a first endless flexible belt seated in said grooves and linking said two pairs of plates, said belt having a generally V-shaped cross section; driven means rotated by said second pair comprising a pulley member coaxially mounted with said second pair and secured to rotate therewith, a second pulley member, and second,

endless flexible belt linking said first and second pulley members, the assembly of said second pair of plates and said first pulley member being pivotally mounted on said base with said second belt member determining said predetermined distance of said second pair of plates from said first pair; spring means biasing said assembly of said second pair and said first pulley away from said first pair and from said second pulley, said pivotal mounting of said assembly of said second pair and said first pulley being arranged to permit a predetermined amount of movement of said second pair of plates away from said first pair in response to the proportional stretching of said first and second belts due to aging thereof; means for axially moving one plate of one of said pairs relative to the other plate thereof for changing the depth at which said belt is seated in the groove formed by said one pair thereby to vary the speed of rotation of said second pair; means yieldably biasing the plates of the other of said pairs toward each other to correct their spacing in response to an axial adjustment of said one pair; and means adjacent one of said pairs for controlling said means for axially moving one plate to provide return of said second pair to a particular speed regardless of belt wear, said control means sensing the distance from the center of rotation of the pair to which it is adjacent to the outer surface of said belt where it is seated in the groove formed by said adjacent pair and stopping said means for axially moving one plate when said distance is a predetermined amount.

References Cited in the file of this patent UNITED STATES PATENTS 2,127,031 Johnson et al. Aug 16, 1938 2,139,482 Atz Dec. 6, 1938 2,589,897 Turnbull Mar. 18, 1952 2,619,736 Geldhof Dec. 2, 1952 2,638,006 Feustel May 12, 1953 FOREIGN PATENTS 1,147,443 France June 11, 1957 

